The primary objective of this application is to identify essential oromotor skills that children obtain during early speech development and factors that contribute to individual variation in the course of speech development. The specific aims are (1) to identify the movement characteristics of prespeech orofacial behaviors, (2) to identify developmental changes in articulatory performance that underlie early phonetic ability, (3) to identify speaker factors that influence the rate of early speech motor development, and (4) to identify the articulatory characteristics of infant-directed speech. Thirty children will be studied longitudinally every 3 months from 3 to 33 months of age. At each age, measures of oromotor performance, phonetic ability, craniofacial growth, receptive and expressive language development, and general-motor development will be gathered. An optical motion-capture system will be used to quantify developmental changes in craniofacial size and orofacial kinematics for a wide range of speech and non-speech behaviors. Orofacial kinematic data will also be collected from each child's caregiver during infant-directed and adult-directed speech to examine the potential relationship between parental articulation style and early articulatory performance. Latent growth modeling will be used to characterize individual patterns of development in speech and oromotor performance and to quantify the strength of association between the rates of growth in oromotor performance, phonetic ability, and skills in other developmental domains. This study will provide essential information regarding the developmental course of early articulatory development and the influence of physiologic, anatomic, and linguistic processes on early speech development. These normative descriptions will serve as reference data for gauging the degree of impairment in children with speech motor disorders, and will provide developmentally appropriate guidelines for speech-treatment focused on improving underlying movement competencies.